OBJECTIVES: To determine the incidence of progressive internal carotid artery (ICA) stenosis by head and neck contrast-enhanced computed tomography (CT) in 82 patients who underwent surgery, chemotherapy, or combination therapy for oral squamous cell carcinoma (OSCC). METHODS: The study included 82 patients who underwent head and neck contrast-enhanced CT after surgery alone or combined surgery and chemotherapy for OSCC at the Department of Oral and Maxillofacial Surgery of Ichikawa General Hospital, Tokyo Dental College, or Tokyo Dental College Oral Cancer Center between December 2002 and March 2010. RESULTS: Comparison with previously obtained head and neck contrast-enhanced CT images revealed progressive arterial stenosis of the ICA in five patients with a mean age of 62.0 years. All five patients were male, and their OSCC sites were the tongue in two, the floor of the mouth in two, and the mandibular gingiva in one. Tumor resection and neck dissection were performed for four patients and tumor resection alone for one patient. Four patients underwent chemotherapy. ICA stenosis occurred on the same side as the tumor in all five patients. CONCLUSIONS: The results of this study suggest that, given the possibility of post-treatment vascular events, attention must be paid to subsequent changes in the ICA over time. The results also indicate the usefulness of head and neck contrast-enhanced CT in identifying such problems.